This phrase is from Hamlet. I always though it meant something like “stabbed with your own sword” or maybe “lifted up on your own spear.” It DOES mean“injured by the device that you intended to use to injure others.”However, a petard is not a sword or spear, as I mistakenly thought, but rathera box filled with gunpowderthat was used in siege warfare to blast down a door or make a hole in a wall.

To hoisemeans“to lift or raise”, which is what happens to a person who sets off his own explosive device by accident.

A modern-day example

A petard can also be a kind of firework.

I’m going to spare you any graphic images of fireworks injuriess.They’re really gruesome.

“[To the Church in Laodicea] “To the angel of the church in Laodicea write: These are the words of the Amen, the faithful and true witness, the ruler of God’s creation. Here I am! I stand at the door and knock. If anyone hears my voice and opens the door, I will come in and eat with that person, and they with me.”